1. Field of the Invention
The present invention relates to novel straight-chain aromatic poly(amideimide)s in which the polymer chains have functional endgroups, each comprising a latent maleimide function.
This invention also relates to a process for the preparation of such novel poly(amideimide)s having functional endgroups, and to the production of crosslinked polymers therefrom.
As utilized herein, by the expression functional endgroup comprising "a latent maleimide function" is intended a radical containing a blocked maleimide function which, under the conditions existing at the beginning of subsequent conversion of the poly(amideimide)s of the invention, under the influence of heat, is converted into a free maleimide function of the formula: ##STR1## (reaction designated "thermal deblocking of maleimide functions").
2. Description of the Prior Art
Poly(amideimide)s having functional endgroups comprising a latent maleimide function, such as a nadimido (or 3,6-endomethylene-1,2,3,6-tetrahydrophthalimido) residue, are described in Japanese Application JA-A-50/089,499, which poly(amideimide)s are prepared by the following reaction sequence: a polycondensation reaction in solution between, in particular, a monoanhydride of a tricarboxylic acid and an excess of an aromatic diprimary diamine, followed by a condensation reaction of nadic acid (or 3,6-endomethylene-1,2,3,6-tetrahydrophthalic acid) with the NH.sub.2 endgroups of the oligomers formed upon completion of the polycondensation reaction.
However, the actual carrying out of such a process presents several disadvantages. One of these disadvantages, which is common to the majority of processes in which a reactive amine is reacted with a carbonyl-containing organic compound, such as an anhydride of a carboxylic acid, is in the necessity for conducting a cyclizing dehydration of the poly(amideacid)s formed as intermediates; as this reaction is an equilibrium reaction, it is necessary to remove the water liberated and this cyclizing operation generally cannot be carried out completely in solution.
Another disadvantage, which results from the impossibility of, or at least the great difficulty in, obtaining a complete cyclization of the poly(amideacid)s formed as intermediates, is in the development of secondary reactions, in which the non-cyclized poly(amideacid)s interfere, which are responsible for imperfectly providing functional endgroups on the poly(amideimide) chains which contain a nadimido residue and for an increase in the molecular weights. The result is great difficulty, if not impossibility, in being able to use these polymers (after thermal deblocking of the maleimide functions), at temperatures equal to or below 300.degree. C. and at pressures equal to or below 10 MPa, to produce, for example, suitable shaped articles by compression molding.